Heretofore, introduction of medication at a preferred site within the body of a patient has been accomplished through delivery structure in either of essentially two forms, namely, injection through a needle or infusion through a catheter. Each of these methodologies has resulted in delivery of medication primarily to a location immediately adjacent to the distal tip of the needle or catheter. After injection through a needle or infusion through a catheter, the medication is absorbed into, or spreads by osmosis to, the tissues immediately adjacent to the discharge orifice of the needle or catheter, or the absorption field, for localized treatment. The medication then in varying degrees migrates with the normal circulatory and other systems of the body until fully metabolized systemically.
As the migrating medication is dispersed, inefficiencies in treatment may result. Significant factors in this context include the particular medication selected and, in part due to the varying size of treatment sites causing pain, the varying number of pain receptors to be blocked from patient to patient. For example, treatment sites that require a more concentrated dosage of a given medication may receive a preferred dosage concentration for a short period of time after which, as the medication is dispersed systemically, the treatment site is supplied a dosage concentration that is lower than that preferred. The dosage concentration must be sustained at a level sufficient to maintain a concentration gradient that reduces or eliminates the pain in the treatment site so long as it is desirable to do so. In some instances, excessive doses have been utilized to compensate for this dispersion effect, inherently resulting in exposure of the treatment site to unnecessary levels of medication. Such exposure not only wastes medication that may be expensive, but may also have a detrimental impact on the surrounding tissue as well as precipitating adverse side effects in other aspects of the patient's systemic physiology.
Another challenge imposed by the foregoing dispersion conundrum involves the rate and frequency of introduction of medication to surgical and general treatment sites. Historically, when a patient has required a medical treatment, it has been necessary for the patient to travel to the facilities of the medical practitioner rendering such treatment. The logistical difficulties of scheduling and commuting have discouraged patients from maintaining an optimal treatment regime. There has been a tendency, where practicable, to increase the dosage of some injected or infused medications, whereby to compensate for less frequent visits. With the onset of the prevalence of patient home treatment systems, this inefficiency is being addressed by the use of portable, patient-operated pumps in accordance with physician-directed protocols.
A technical difficulty exists with respect to the accuracy of the placement of the medicinal delivery orifice relative to the desired treatment site. It has not always been clear how far a needle or catheter should be inserted into a body to optimize the likelihood that the discharge orifice is ideally positioned to deliver medication, within an acceptable degree of precision, to the treatment site. Use of flexible catheters allows for potential migration of the catheter to a range of subdural or intra-cavity positions that may be undesirable, increasing the desirability of a more rigid delivery structure with means for monitoring depth of insertion.
A specific problem associated with infusion drug delivery through plural port catheters (e.g., “soaker catheters”) is the inherent differences in the “flow through” characteristics of each of a plurality of discharge orifices. Uniformity in the infusion rate among the plurality of discharge orifices cannot reasonably be expected
Material prior art structures are presently available from such companies as I-Flow Corporation of Lake Forest, Calif., Micor, Inc. of Allison Park, Pa., Cook Medical of Denver, Colo., and Medical Profiles, Inc. of Livonia, Mich. C.R. Bard, Inc. of Murray Hill, N.J., has dealt with soaker catheter technology involving striations but has delivered medicaments to each striation through an individual lumen to achieve uniform flow rates to a plurality of discharge orifices. I-Flow, for example, has designed a Soaker™ Catheter to infuse drugs over an area that is wider than that of point-source catheters, which deliver only at a single, discrete location. The Soaker™ Catheter device is being used intraoperatively primarily for large abdominal and chest incisions to relieve postoperative pain.
Less related but instructive prior art includes U.S. Pat. Nos. 5,834,001 to Dionne et al., entitled “Methods for Making Immunoisolatory Implantable Vehicles With a Biocompatible Jacket and a Biocompatible Matrix Core”; 5,807,306 to Shapland et al. entitled “Polymer Matrix Drug Delivery Apparatus”; 5,773,577 to Cappello entitled “Products Comprising Substrates Capable of Enzymatic Cross-linking”; and 4,450,150 to Sidman entitled “Biodegradable, Implantable Drug Delivery Depots, and Method for Preparing and Using the Same.” These patents teach implantable modules for gradual, time release introduction of medication as one approach to treatment of various conditions over a larger absorption field.
Similarly, remote systems instructive in concept are disclosed in U.S. Pat. Nos. 5,299,885 to Prassas et al. and its progeny 5,474,398 entitled “Stabilized Porous Pipe”; 5,374,138 to Byles entitled “Subsurface Irrigation Apparatus and Method”; 5,368,235 to Drozdoff et al. entitled “Soaker Hose Assembly”; 5,285,968 to McSheehy entitled “Water Distribution Yoke for Tree Cultivation”; and 4,168,799 to Turner entitled “Soaker Hose.”
A need remains for an efficient means of introducing medication to a treatment site of a size larger than the absorption field immediately surrounding the discharge orifice of a needle or catheter. The need would be beneficially addressed, at least in part, by provision of a plurality of discharge orifices spaced and positioned relative to each other along a distal portion of a tubular element for optimal dispersion of medication across a range of proximal absorption fields. Such orifices may be beneficially structured and arranged as striations.
A further need exists for a means of ratably introducing medication in increments and at intervals tailored to the optimal demands of any given selected treatment dosage, regime and protocol. Such a means would desirably allow for the patient, relative to his or her measured condition, to influence determination of the timing and nature of such treatment.
A need also exists for a simple means of placing a therapeutic medicinal tubular element with optimal accuracy at a treatment site. A patient diffusion and perfusion system wherein the desired depth of insertion of the tubular element can be determined visually by external viewing of the tubular element itself, thereby enabling facile location of a pain site to be treated, would be desirable.